Process for preparing a UV-curable coating material and anti-abrasion coating composition

Abstract

Disclosed is a process for preparing a UV-curable coating material comprising the steps of effecting a hydrolysis reaction of (a-1) 40 to 90 parts by weight of colloidal silica, and (a-2) 60 to 10 parts by weight of a hydrolyzate of an alkoxy silane compound containing not less than 50% by weight of a compound of the formula (I) <IMAGE> (I) replacing the dispersion medium of the colloidal silica with a nonpolar solvent when the amount of dehydration is in the range of 50 to 90% of theoretical value; and effecting a further condensation reaction while maintaining in the state of 30 to 90% by weight of solid components in the presence of the nonpolar solvent. A coating composition containing the UV-curable coating material can form an anti-abrasion-coating film having excellent abrasion resistance, surface smoothness, thermal resistance, chemical resistance, durability, weather resistance and adhesion to the substrate.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. A process for preparing a UV-curable coating material comprising the steps of effecting a hydrolysis reaction of (a-1) 40 to 90 parts by weight (on a solid basis) of colloidal silica wherein the dispersion medium is a polar solvent, and (a-2) 60 to 10 parts by weight of a hydrolyzate and/or hydrolyzed and partially condensed product of an alkoxy silane compound containing not less than 50% by weight of a compound of the general formula (I) ##STR3##  wherein X is CH 2  ═CH--COO--, CH 2  ═C(CH 3 )--COO-- or CH 2  ═CH--, R 1  is a direct bond or an alkylene group having 1 to 8 carbon atoms, R 2  and R 3  are alkyl groups having 1 to 8 carbon atoms, a is a whole number of 1 to 3, b is a whole number of 0 to 2, and (a+b) has a value of 1 to 3;   replacing the dispersion medium of the colloidal silica with a nonpolar solvent when the amount of dehydration is in the range of 30 to 90% of theoretical value; and   effecting a further condensation reaction while maintaining in the state of 30 to 90% by weight of solid components in the presence of the nonpolar solvent.   
     
     
       2. An anti-abrasion coating composition consisting essentially of (A) 5 to 70 parts by weight (on a solid basis) of the UV-curable coating material prepared by the process of claim 1,   (B) 30 to 95 parts by weight of a polyfunctional monomer having two or more (meth)acryloyloxy groups in the molecule,   (C) 0.01 to 5 parts by weight of a photopolymerization initiator,   per 100 parts by weight of the combined amount of components (A) and (B).   
     
     
       3. An anti-abrasion coating composition of claim 2 which further contains (D) 0.1 to 20 parts by weight of an ultraviolet light absorber, and   (E) 0.1 to 5 parts by weight of a hindered amine type light stabilizer,   per 100 parts by weight of the combined amount of components (A) and (B).